Power over Ethernet (PoE), in accordance with both IEEE 802.3af-2003, and IEEE 802.3at-2009, each published by the Institute of Electrical and Electronics Engineers, Inc., New York, the entire contents of each of which is incorporated herein by reference, defines delivery of power over a set of 2 twisted wire pairs without disturbing data communication. The aforementioned standards particularly provide for a power sourcing equipment (PSE) and a powered device (PD). IEEE 802.3af-2003 is referred to herein as the “af” standard and IEEE 802.3at-2009 is referred to herein as the “at” standard.
The “af” standard limits the amount of power provided over a set of 2 twisted wire pairs to a PD to 12.95 watts, and the “at” standard limits the amount of power provided over a set of 2 twisted wire pairs to a PD to 30 watts. If power is provided over 4 twisted wire pairs, which is not covered the above two standards, up to 60 watts of power can be provided to a PD.
In order to improve overall system power and load management, the “af” standard provides for PD classification to one of 4 potential classes. Each class exhibits a range of maximum power drawn by the PD. The “at” standard further provides for an additional class. Particularly, class 0 is defined as a default class in which no power requirement information is supplied by the PD and thus the PSE is required to provide up to 15.4 watts to the PD. For a class 1 PD, the PSE is required to supply power of up to 4 watts. For a class 2 PD, the PSE is required to supply power of up to 7 watts. For a class 3 PD, the PSE is required to supply power of up to 15.4 watts. For a class 4 PD, the PSE is required to supply power of up to 30 watts. As described above, the “at” standard allows for a maximum power supply of 30 watts over 2 twisted wire pairs and utilizing 4 twisted wire pairs thus allows supply of up to 60 watts of power. Unfortunately, only a single class is provided for all high powered devices with power requirements of 15.4-60 watts. Therefore, power and load management cannot be provided for high powered devices.
What is needed, and not supplied by the prior art, is a method of classification for high powered devices which is unambiguous, is compatible with prior art classification under the “af” and “at” standards, and conforms to both the PD and the PSE the characteristics of the coupled device.